1. Field of the Invention
The present invention relates to an apparatus which adjusts exposure using luminance values of a plurality of blocks consisting of at least one pixel that constitute a photoelectrically converted image pickup screen.
2. Description of the Related Arts
Up to now, an apparatus of this type which adjusts exposure so that an average luminance value of an image pickup screen at the time of photometry can reach a target luminance value (luminance value for reflectivity of 18%) has been proposed. In this apparatus, after luminance values of a plurality of blocks which constitute the image pickup screen have been respectively calculated, photographing is enabled with an appropriate exposure by obtaining these averages as an average luminance value and adjusting exposure so that this average luminance value can reach the target luminance value. Moreover, in addition to this, an apparatus (for example, Japanese Patent Publication No. Hei 7-26874) which tries to realize accurate photometry by performing preliminary photometry and practical photometry so that the luminance range of an object screen can be within the luminance range in which photometry of a CCD is enabled is also proposed.
However, in such apparatus, monochromatic light may be displayed more brightly than needed. This is based on the fact that as the proportion of monochromatic light (for example, red) to an image pickup screen at the time of photometry increases, an average luminance value of the image pickup screen decreases and exposure is adjusted so that this average luminance value can reach a target luminance value. This becomes a cause which results in the color saturation of a display apparatus such as a CRT, and a sense of incompatibility may be generated in those who watch this display apparatus. Further, there was a drawback that if achromatic light, for example, a white portion (reflectivity of about 90%) can be seen in an image pickup screen at the time of photometry, white is displayed darkly due to the correction of exposure to a target luminance value, and, conversely, if a black portion (reflectivity of about 3%) can be seen in the image pickup screen, black is displayed brightly due to the correction of exposure.
An object of an apparatus of the present invention is to enable photographing with a more appropriate exposure.
An apparatus of the present invention employs the following means to attain the aforementioned object.
A first apparatus of the present invention is an apparatus for adjusting exposure using luminance values of a plurality of blocks consisting of at least one pixel that constitute a photoelectrically converted image pickup screen, comprising reference luminance value calculating means which calculates reference luminance values of the plurality of blocks sorting means which sorts the plurality of blocks into blocks belonging to monochromatic light and blocks belonging to light other than the monochromatic light luminance value setting means which sets higher values than the reference luminance values calculated by the reference luminance value calculating means as the luminance values of the blocks belonging to the monochromatic light among the sorted plurality of blocks and sets the reference luminance values calculated by the reference luminance value calculating means as the luminance values of the blocks assigned to the light other than the monochromatic light; and exposure adjusting means which adjusts exposure based on the set luminance values.
In a first apparatus of the present invention, reference luminance value calculating means calculates reference luminance values of a plurality of blocks, and sorting means sorts a plurality of blocks into blocks belonging to monochromatic light and blocks belonging to the light other than the monochromatic light. Then, luminance value setting means sets higher values than the reference luminance values calculated by the reference luminance value calculating means as the luminance values of the blocks belonging to the monochromatic light from the plurality of blocks sorted by the sorting means, sets the reference luminance values calculated by the reference luminance value calculating means as the luminance values of the blocks belonging to the light other than the monochromatic light and exposure adjusting means adjusts exposure based on the set luminance values. According to this first apparatus of the present invention, since the luminance values of the blocks assigned to the monochromatic light are set higher than the reference luminance values and exposure is adjusted based on these set luminance values, the monochromatic light can be prevented from being brighter than needed, and, as a result, photographing is enabled with a more appropriate exposure.
In such a first apparatus of the present invention, the sorting means can also be made a means which sorts a plurality of blocks based on signal ratios of RGB (red, green and blue) signals in the blocks.
Further, in the first apparatus of the present invention, the luminance value setting means can also be made a means of setting the maximum signal value among elements of RGB signals as the luminance values of the blocks belonging to the monochromatic light.
A second apparatus of the present invention is an apparatus for adjusting exposure using luminance values of a plurality of blocks consisting of at least one pixel that constitute a photoelectrically converted screen, comprising sorting means which sorts the plurality of blocks into at least two groups using a threshold regarding a predetermined color luminance value correction means which corrects the luminance values of the plurality of blocks using a predetermined weight which corresponds to the sorted groups; and exposure adjusting means which adjusts the exposure based on the corrected luminance values.
In the second apparatus of the present invention, sorting means sorts a plurality of blocks into at least two groups using a threshold regarding a predetermined color, and luminance value correcting means corrects luminance values of a plurality of blocks using a predetermined weight which corresponds to the sorted groups. Then, exposure adjusting means adjusts exposure based on corrected luminance values. According to this second apparatus of the present invention, since luminance values are corrected in accordance with the color information of an image pickup screen, photographing is enabled with a more appropriate exposure in accordance with the conditions of an object.
In a second apparatus of the present invention, the sorting means can also be made a means which sorts a plurality of blocks based on signal ratios of RGB signals in the blocks.
Moreover, in a second apparatus of the present invention, the threshold regarding the predetermined color can be a threshold in which a plurality of blocks are sorted into a block belonging to achromatic light, a block belonging to monochromatic light and a block belonging to normal light other than the achromatic light and the monochromatic light. In the second apparatus of the present invention according to this aspect, the luminance value correcting means can be a means which uses a great weight in the order of the block belonging to the achromatic light, the block belonging to the normal light and the block belonging to the monochromatic light. Thus, since exposure is adjusted by preferentially evaluating an object having a tone and low evaluating the achromatic color, the effect caused by the achromatic light can be reduced when adjusting the exposure, and, as a result, photographing is enabled with a more appropriate exposure.